1. Field of the Invention
The present invention generally relates to a process of forming a semiconductor device, and more particularly to a process of forming a complementary metal-oxide-semiconductor (CMOS) image sensor with reduced photolithography process.
2. Description of Related Art
Image sensors are used to detect an image by converting, for example, light into electrical signals, and are widely adopted in electronic devices such as cameras. FIG. 1 shows a simplified flow diagram illustrating a typical process of manufacturing CMOS image sensors. In the illustrated flow, each photolithography step defines an area where a portion of a device is to be implanted. Multiple repetitions of the photolithography step and succeeding implant step are required to construct an entire device.
Photolithography is a process used to pattern parts of a semiconductor device such as the image sensor. Photolithography is generally performed by photoresist application, exposure, development and removal. As tens of photolithography steps are required to construct an entire device, they incur substantive manufacturing cost and cycle time.
In order to bring manufacturing cost lower and thus to gain higher profit margin, a need has arisen to propose a novel scheme for manufacturing an image sensor in a cost-effective manner.